Dehydrohalogenation of halobicyclo compounds



United States Patent Y DEHYDRGHALOGENATION F HALOB'ICYZLQ iCOM-PGUNDS Lou'is 'SchmerIingRiverside, Ill., assig'noryby mesne assignments, to Universal Uil "Products Company, Des 'Plaines, "Ill a corporation of Delaware No Drawing. Application April as, "1956 Serial No.358ih469 iffliaims. (Cl. 260-648) This application .is a continuation-in-part of my ,coending' application ."Serial No. 342,753, which was filed March I6, 1953, and now abandoned.

'The' present invention relates to methods for dehydro'ha'logenating certain polyhaTlobicyclo-olefinic compounds.

Heretofore 'it has been indicated that bicycloalkadienes could not be prepared 'by dehatlogenating hallohicyclm alkenes obtainedby the condensation of a cyclo'alkadiene with ahaloole'fin. On the other hand, partial .dehalogenation of the condensation product of a halogenated cycloalkadiene, namely"hexachlorocyclopentadiene, and vinyl chloride may be carried out:

Q1 01 i 'KOH O1 CLOCI 1.0.1 01' or Anon"! 0,1 O1 G1 ditions \of ,prior processes, the .single.halogen .atom being .tooinert to undergo reaction with the =deh ydrohalogenating .agent. For example, attempts have been made, as disclosed in a paper by Roberts .et .al., Journal of .the vAmerican Chemical Society, 72, .3329 (1950.), and in Belgian Patent "No. 498,176 "issued to J. Hyman et :al., to dehydrochlor'inate S-chlorobicyclo'[2.2.1]12 hepteue t0 form 'bicyclo [2.2.1]-.2,5-heptadiene. This is illustrated by the following equation:

1 have .-found that the products ofthe condensation :of cycloal-kadienes with aparticul'ar class-of =haloolefiuseonactive halogens and may be partially dehalogenated to the desired halobicycloalkadienes.

:It is, therefore, an object aof this invention to prepare a :halobicycloalkadiene byadehydrohalogenatingamolyhalobicycloalkene.

,Afurther object ofthis [invention is -.to ifirst prepare-a polyhalobicycloalkene and dehydrohalogenate the same to form a ihalobic ycloalkadiene.

.One embodiment oftthis invention ,is foundin-aprocess K031 N 0 reaction .Alcohol for the preparation of a halobicycloalkadiene whichcom- ,pris,es reacting a conjugated .cycloalkadiene with va .polyhaloolefin'having .the general formula 2,914,571- Patented Nov. .24 19.59

in which X is ahalogen radical and Q is .a radical selected from the group consis'tingof hydrogen, halogen, alkyland 'haloalkyl radicals thereby forming a polyhalohicycloalkene containing atleast one "halogen atom on ieachof two adjacent carbon atoms, de'hydrohalogenating :said polyhalobicyc'loalkenein the presenceof a dehalogenating agent to form a halobicycloalkadiene, and recovering the latter compound.

A specific embodiment of this invention resides in a process for the preparation of .a halobicycloheptadiene by reacting cyclopentadiene with a polyhaloethylene containing at least one halogen atom on each of the two adjacent carbon atoms thereby iforming a :polyhalobicycloheptene containing :at least 'one halogenratom on'each of the two adjacent carbon atoms, .dehydrohalogenating said polyhalobicycloheptene in :the presence of a dehydrohalogenating agent to form a halobicycloheptadiene,:and recovering the later compound.

A more specific embodiment o'f the invention resides in a process for preparing 2-chloro'bicyclo [2.2.1]-2,5-heptadiene which comprises reacting cyclopentadiene with ,1 ,2-dichloroethylene to [form 5,6dichlorobicyclo [212.4'3-

2-heptne, .dehydrohalogenating said compound in the .presence.of potassium hydroxide and methanol :to form 2-.chlorobicyclo -,[2.2.1l-2,5-heptadiene, and recovering the lattercompound.

Yet another vspecific embodiment of the invention :1:- sides in a process for preparing 2-ichlorobicyclo "[22:11- 2,5heptadiene by dehydrohalogenating 5,;6-dichlorobioyolo 2.2.1] -2 heptene in the presence {of potassium hydroxide and ethanol to form Z-chlorobicyclo [2.2.:L],2,51heptadiene, and recovering the latter compound.

Other objectsand embodiments referring towalternative reactants utilizable ,asrcharging'stocktinithe present process and to alternative dehydrohalogenating agents within the scope of the invention will be referred to in greater detail in the following further detailed description of the invention.

As hereinbefore set forth it has now been discovered that halobicycloalkadienes having the following formula:

R Q l t in which X represents a halogen radical, .Q represents afhydrogen, halogen, alkyl or 'haloalkyl radical, y isxan integer from 1 to 4, preferably .1 or 2, and -R is lindepen'clently selected from lthe group consisting ofhydrogen and alkyl radicals may be synthesized by reacting. nicotijugated cycloalkadiene with a polyhaloolefin having the general formula: v

Q a .H

in which X represents a halogen radical and Q represents a hydrogen, halogen, alkyl orhaloalkyl radical to form a polyhalobicycloalkene, and dehydrohalogenating the resulting compound thus yielding the desired halobicycloalkadiene. The reaction between the conjugated cyclo- 'alkadiene andfthe polyhalodlefin fis'a thermal condensat'ion -anduccurs"in the absence of any added catalyst. In addition the reactants are preferably present .-in a molar ratio 'range of from about 0.5:1 to about 019::1 mole of cycloalkadiene to polyhaloo'lefin. Theexcess of polyhaloolefin is preferred in order to insure the production "of a bicyclic compound instead of ,a 'tetracyiclic compound which'may occur if the tcycloalkadiene is excess. The haldbicycloalkadienes which are the desired products of the "invention are useful as intermediates in the preparation of insecticides, pharmaceuticals, resins When cyclopentadiene is used as a feed stock, the reaction using a 1,2-dihaloethylene will proceed according to the following equation:

. The dihalobicycloheptene will then be dehydrohalogenated by means of a dehydrohalogeuating agent such as an alkali metal hydroxide and an alcohol according to the following equation to prepare the monohalobi- C y cloheptadlenei i m 2 I l/ In the above equation X is a halogen, MOH is an alkali metal hydroxide and ROH is an alcohol.

A more specific example of the above method of preparing a halobicycloheptadiene is found in the following equations in which cyclopentadiene is reacted with 1,2-dichloroethylene and the resulting compound, comprising 5,6-dichlorobicyclo[2.2.1]-2-heptene, is dehydro halogenated with potassium hydroxide in an ethyl alcohol medium to form the desired Z-chlorobicyclo [2.2.11- 2,5-heptadiene.

1 mam.

MOH

ROH

Q and X representing radicals hereinbefore set forth may include 1,2-dichloroethylene, 1,2-dibromoethylene, 1,2-difluoroethylene, 1,2-diiodoethylene, 1,1,2-trichloroethylene, 1,1,2-tribromoethylene, 1,1,2-trifluorethylene, 1,1,2-triiodoethylene, 1,2-dichloro-l-propene, 1,2,3-trichloro-l-propene, 1,2-dibromo-1-propene, 1,2,3-tribromol-propene, 1,2-difluoro-1-propene, 1,2,3-trifluoro-1-propene, 1,2-diiodo-1-propene, 1,2,3-triiodo-1-propene, 1,2- dichloro-l-butene, 1,2,4-trichloro-1-butene, 1,2-dibromol-butene. 1,2,4-tribromo-1-butene, 1,2-difluoro-l-butene,

1,2,4-trifluoro-l-butene, 1,2-diiodo-l-butene, 1,2,4 triiodo-l-butene, 1,2-dichloro-1-pentene, 1,2-dibromo-lpentene, 1,2,5,5-tetrachloro 1 pentene, 1,2,5,5-tetrabromo-l-peutene, 1,2-difluoro-l-pentene, l,2,5,5 -tetrafiuoro-l-pentene, 1,2-diiodo-1-pentene, 1,2,5,5-tetraiodol-pentene, etc. It is to be understood that the above enumerated conjugated cycloalkadienes and polyhaloolefins of the aforesaid general formula are only representatives of the compounds which may be used, and that this invention is not necessarily limited thereto.

The dehydrohalogenation of the polyhalobicycloalkenes resulting from the reaction between the conjugated cycloalkadiene and the polyhaloolefin is effected by treating said compounds with a dehydrohalogenating agent which includes the hydroxides of the alkali metals and alkaline earth metals such as the hydroxides of lithium, sodium, potassium, rubidium, cesium, calcium, barium and strontium; amines such as. trimethylamine, pyridine, quinoline, etc.; alkali metal alkoxides such as sodium methoxide, potassium ethoxide, etc.; and other basic substances such as potassium carbonate, potassium phenoxide, etc. The hydroxides of the alkali metals and alkaline earth metals may be used as such (fused or powdered) or they may be dissolved in a suitable organic solvent preferably an alcohol. The particular alcohol which is used as the organic solvent in the dehydrohalogenating reaction will depend largely upon the temperature at which the reaction occurs. Alcohols which are utilizable in this reaction include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, amyl, etc.

The operating conditions under which the process of the present invention is conducted will, to' some extent, depend upon the particular compounds employed in the reaction. The temperature for the reaction between the particular conjugated cycloalkadiene and the polyhaloolefin in which a polyhalobicycloalkene is formed will range from about atmospheric to about 250 C. or more, the preferred range being from about to about 200 C. Likewise, the dehydrohalogenation step of this process will also occur at temperatures depending upon the particular reactants and the solvent which is used as a medium for the reaction. Suitable temperatures will usually lie in the range of from about 50 to about 250 C., the preferred range being from about 75 to about 200 C. In addition, the reaction will usually take place at atmospheric pressure; however, when the reaction temperature is in a higher range than the boiling point of the solvent, superatmospheric pressures may be employed.

The process of this invention may be effected in any suitable manner and may comprise either a batch or a continuous type operation. When a batch type operation is used, a quantity of the reactants comprising the conjugated cycloalkadiene and the polyhaloolefin is placed in a reactor provided with a mixing and heating device. The reactor is heated to the desired temperature while thoroughly admixing the contents thereof. After a suitable period of time has elapsed, the reactor and its contents are cooled to room temperature, after which the desired prodnet is recovered by suitable means, for example, by fractional distillation or other means known in the art, While the unreacted feed stock may be recharged to form a portion of the starting material of the next hatch. The desired product is then placed in a second reactor, or if so desired, returned to the same reactor and the dehydrohalogenating agent (and organic solvent, if used) added thereto. The reactor is then heated to the desired temperature until the reaction is completed, after which the halobicycloalkadiene is separated by suitable means hereinbefore set forth.

Another method of operation of the present process is of the continuous type. In this operation the reactants comprising the conjugated cycloalkadiene and the polyhaloolefin are continuously charged to a reactor provided with heating and mixing means. The reactor may com- The desiredreactiomproduct comprising a polyhalobicycloalkene is continuously withdrawn from this vessel by suitable means and charged into a second reactor also maintained at suitable operating conditions, while the unreacted feed stock from the first reactor may be withdrawn and recycled for use as a part of the fresh feed stock. The dehydrohalogenating agent, comprising for example, an alkali or alkaline earth hydroxide, either in solid or fluidized form or dissolved in the solvent which acts as a medium in which the dehydrohaloge'nation takes place are also charged to the aforesaid second reactor by suitable means. The dehydrohalogenated compound, comprising a halobicycloalkadiene, is continuously withdrawn from this second reactor and purified by conventional means hereinbefore set forth, while the unreacted material may be recycled to form a .portion of the feed stock.

As hereinbefore set forth the halobicycloalkadienes prepared in the above manner may be reacted with a polyhalocycloalkadiene such as hexachlorocyclopentadicue to form polyhalotetracyclic compounds which are useful as insecticides. The condensation of the halobicycloalkadiene and the hexachlorocyclopentadiene is carried out in a similar manner to the reaction between the conjugated cycloalkadiene and the polyhaloolefin containing at least one halogen atom on each of the doubly bonded carbon atoms as hereinbefore described. The temperature at which the reaction is to be carried out will be in the range of from about atmospheric to about 250 C. or more, the preferred range being from about 60 C. to about 200 C. In addition, the reaction may be elfected in any suitable manner, ether a batch or a continuous type operation similar to that hereinbefore described with reference to the reaction between the cycloalkadiene and the polyhaloolefin. In the batch type operation the reactants comprising the hexachlorocyclopentadiene and the halobicycloalkadiene are placed in a reactor provided with heating and mixing devices. This reactor is heated and maintained at the desired temperature until the reaction is completed after which the reactor is cooled to room temperature and the desired reaction product withdrawn, separated and purified by conventional means such as fractional distillation, crystallization, etc.

When a continuous type operation is used the reactants may be introduced into a reactor through lines provided therefore, said reactor being equipped with heating and mixing means and maintained at the desired operating conditions of temperature and pressure. The desired product is withdrawn and purified while the unconverted material may be recycled and used as part of the feed stock, or mixed with fresh starting materials. It is also contemplated within the scope of this invention, that this latter reaction may take place in the presence of inert diluents, e.g. liquid aromatic hydrocarbons such as benzene, toluene, etc.

The present invention is further illustrated with respect to specific embodiments thereof in the following examples which, however, are not intended to limit the general- 1y broad scope of the present invention in strict accordance therewith.

Example I This example shows the preparation of 2,3-dichlorobicyclo[2.2.1]-2,5-heptadiene by the partial dehalogena- I tion of 5,5,6-trichlorobicyclo[2.2.1]-2-heptene using a dehydrohalogenation agent comprising an alkali metal hyphen'es of additionalpressure at approximately: 180 C. for aperiod of six" hours. Atthe end of this time: the vessel and'itscontents were cooled toroom temperature, the reaction products consisting of 296 g. of an amber liquid. The liquid was taken'upi n pentane; washed with dilute alkali and water, dried and subjected to fractional distillation. A. yield of 83 g. of a material boiling at 85- 87 C. at 7.5 mm. pressure was obtained. This material became partially crystalline upon standing, filtration of this product yielding 25 g. of a crystalline material melting at 51 C. and 26 g. of an oil, said oil and crystalline material apparently being stereoisomers. The crystals and oil were subjected to analysis, the results being set forth below.

Analysis.-Calculated for C H Cl (5,5,6-trich1orobicyclo[2.2.l]-2-heptene): C, 42.56; H, 3.57; Cl, 53.87. Found for crystalline material: C, 42.91; H, 3.81; Cl, 53.51. Found for oil: C, 44.36; H, 3.91; Cl, 51.75.

A solution of 20 g. of the crystalline 5,5,6-trichlorobicyclo[2.2.1]-2-heptene and 7 g. of potassium hydroxide in 100 cc. of ethanol was heated under reflux at 80 C. for approximately 30 hours. The reaction product was filtered and a clear amber solution recovered therefrom. This amber solution was treated with water, the insoluble portion taken up in pentane and the resulting pentane solution was Washed, dried and subjected to fractional distillation. There was obtained 5.5 g. of 2,3- dichlorobicyclo [2.2.1]-2,5-heptadiene boiling at 104-105 C. at 92 mm. or 173-l74 C. at 760 mm. pressure.

Example II Another example showing the dehydrohalogenation of 5,5,6-trichlorobicyclo[2.2.1J-Z-heptene using a different solvent as the reaction medium was performed. In this example a solution of 25 g. of 5,5,6-trichlorob'icyclo- [2.2.11-2-heptene and 8 g. of potassium hydroxide in 100 cc. of propanol was heated under reflux at a temperature of approximately C. for 16 hours. The reaction product was filtered, yielding a clear amber filtrate and potassium chloride. The clear amber filtrate was treated with water, extracted with pentane and the extract was washed with water, dried and subjected to fractional distillation under reduced pressure. 9.5 g. of 2,3-dichlorobicyclo[2.2.1]-2,5-heptadiene having a boiling point of 69-70 C. at 22 mm. of 173-174 C. at 760 mm. were obtained and subjected to analysis, the results of which appear below.

Calculated for C H Cl (2,3-dichlorobicyclo[2.2.11- 2,5-heptadiene): C, 52.21; H, 3.75; Cl, 44.04. Found: C, 52.43; H, 3.75; CI, 43.60.

I claim as my invention:

1. A process for the preparation of 2,3-dichlorobicyclo- [2.2.l]-2,5-heptadiene which comprises dehydrohalogenating 5,5,6-trich1orobicyclo[2.2.1]-2-heptene, in the presence of potassium hydroxide and propanol at a temperature of from about 75 to about 200 C. to form 2,3-dichlorobicyclo [2.2.1 -2,5-heptadiene, and recovering the latter compound.

2. A process for the preparation of 2,3-dichlorobicyclo- [2.2.1]-2,5-heptadiene which comprises dehydrohalogenating 5,5,6-trichlorobicyclo[2.2.ll-2-heptene in the presence of potassium hydroxide and ethanol at a temperature of from about 75 to about 200 C. to form 2,3-dichlorobicyclo[2.2.1]-2,5-heptadiene, and recovering the latter compound. 3. A process for the preparation of 2,3-dichlorobicyclo[2.2.1]-2,5-heptadiene which comprises dehydrohalogenating 5,5,6-trichlorobicyclo[2.2.1l-2-heptene in the presence of an alkali metal hydroxide and an organic solvent at a temperature of from about 75 to about 200 C. to form 2,3-dichlorobicyclo[2.2.1]-2,5-heptadiene, and recovering the latter compound.

4. A process for the preparation of 2,3-dichlorobicyclo[2.2.ll-2,5-heptadiene which comprises dehydrohaloa .genating 5,5,6-trichlorobicyc1o[2.2.11-2-l1eptene in the presence of an alkali metal hydroxide and an alcohol at a temperature of from about 75 to ab'outZOO" C.

to form 2,3-dichlorobicyclo[2.2.1l-2,5-heptadiene, and recovering the latter compound.

References Cited "in the file of this pate.

UNITED STATES PATENTS 

3. A PROCESS FOR THE PREPARATION OF 2,3-DICHLOROBICYCLO$2,2,11-2,5-HEPTADIENE WHICH COMPRISES DEHYDROHALOGENATING 5,5,6-TRICHLOROBICYCLO$2.2,11-2-HEPTENE IN THE PRESENCE OF AN ALKALI METAL HYDROXIDE AND AN ORGANIC SOLVENT AT A TEMPERATURE OF FROM ANOUT 75* TO ABOUT 200* C. TO FORM 2,3-DICHLOROBICYCLO$2.2.11-2,5-HEPTADIENE, AND RECOVERING THE LATTER COMPOUND. 